For a number of years we have been studying the regulation of several structural genes that code for enzymes of phosphorus metabolism in Neurospora. We now know of four regulatory genes that exert a high degree of control (greater than 10,000 fold) over the expression of alkaline phosphatase, and are attempting to get more genetic and biochemical insight into how this control is exerted. (1) The work on dosage studies with the regulatory genes will be continued and hopefully completed this year. (2) We will continue trying to get the various structural genes of the "phosphorus family" of enzymes onto the plasmid pBR322, and plan to use the DNA to attempt an isolation of control substances that bind to regions adjacent to the structural genes. There is reason from our genetic work to think that such regions exist, and that the contorl substance coded by the nuc-1 regulatory gene should bind to them. In addition, we hope to use cloned DNA as an analytical tool for following rate of alkaline phospatase mRNA synthesis and degradation in a number of the mutants, and under several different nutritional conditions. (3) We will continue to try to develop a bioassay for the nuc-1 product. (4) We will follow up on Dr. Paszewski's studies of energy charge and changes in types of RNA synthesis during phosphate starvation.